These days, as the virtual reality implementation technology is developed, a user has been forced to want more detailed and realistic information through virtual reality. One of things developed to satisfy the need is a haptic technology which transfers both a sense of touch and force. A simple haptic technology may include a notification function using a vibration motor and is also widely applied to several fields, in addition such as a medical simulator and a game machine etc.
In the future, a haptic device together with a monitor and a speaker are likely to be basically mounted as an output device of a computing device. The reason for this is that there are advantages in that a user's tactile recognition is high and an interoperability with an IT device is excellent by the haptic device installed within a portable electronic device.
Meanwhile, a mobile terminal are taking advantages of portability and to become miniaturization, slivering, grip, and lightening trends by taking portability into consideration and is developed toward multimedia ways in which various functions can be executed. For example, this may become a device which enables a user to perform communication with a counterpart through wireless communication while a user portable the device or a mobile game machine etc., such as Sony PSP or Nintendo DS.
Recently, a mobile terminal have a various functions, such as a smartphone, is being released. A high-performance speaker is installed and one vibration motor is mounted for vibration transfer on such a smartphone.
Furthermore, in order to protect damage to a smartphone that is an expensive mobile terminal, a protective case for a mobile terminal is covered on the outside of the smartphone.
The protective case for a mobile terminal may be formed in the form of a pouch or a protective skin that surrounds the outside surface of a portable electronic device, and can preventing damage attributable to an impact by reducing from the external applied impact. The protective case may be made of a hard or soft materials and may be fabricated in various shapes according to a shape and magnitude so that it is closely attached to the mobile terminal.
Recently, the protective case for a mobile terminal is also developed in a form having a various functions in addition to the protection of damage to a portable electronic device.
For an example, Korean Registration Patent No. 10-970574 has been disclosed “Game Accessory for Mobile Instrument (prior art document)”
In the prior art document, a vibration motor and a large-sized battery are installed in the inner side of the game accessory for mobile instrument, when a user play game is using the mobile device, vibration operating in conjunction with a sound is provided and the large-sized battery is used if the battery of the mobile device is discharged.
However, a linear vibration motor having a rather slow response time is used as the vibration motor disposed in the prior art document. Such a vibration method is insufficient to make a user simultaneous sensory stimulation due to the slow response time, and the form of vibration also remains in simple vibration.
Furthermore, the vibration motor has a little complicated configuration because it has to convert an analog sound source into a digital signal for motor driving to generate vibration that operating in conjunction with a sound.
Moreover, a response time during which a person can feel a simultaneous vibration sense along with visual information must be below 15 ms, but the vibration device of the linear motor method has a response time of 50˜70 ms and is slow in giving a user simultaneous sensory stimulation. A coin type rotary type motor, that is, another example of the vibration motor, has a very slow response time of 100˜150 ms and is merely used for only a notification function for reception.
A tow plane linear motor, that is, another linear motor, is a vibrator using a lateral force fields (LFFs) phenomenon. Furthermore, the plane linear motor has a slowly response time of 50˜70 ms because it is a linear motor using a coil and a magnet, and is thus insufficient in implementing a haptic effect.
As described above, the conventional linear motor and coin type rotary type motor fall into a booming noise phenomenon attributable to a vibration redundancy effect when vibration is continuously generated because the response time and the stop time are slow. Accordingly, simultaneous sensory stimulation corresponding to visual information cannot be felt because a difference between first delivered vibration and subsequently delivered vibration is ambiguous. Furthermore, various vibration patterns, such as strong vibration and micro vibration etc., for a haptic function implementation, cannot be controlled with a very rapid response time.
In the future, as PC game, console game, etc. trend to gradually switch to mobile game, a haptic effect through a mobile terminal may become an important factor. Accordingly, implement a haptic function in a mobile terminal, such as a smartphone having various functions, a rapid response time and precise control of vibration is required and there is a need to develop a haptic technology suitable for game that becomes gradually higher performed.